Antistatic photographic film



G. F. NADEAU ET AL 2,494,054

ANTISTATIC PHOTOGRAPHIC FILM Jane 10, 1950 Filed April 6, L948 EMULSION ANT/STATIC LAYER 0F JU CCINONITRILE EMULSION SUPPORT BALE F. NADEAU 'WALTER .R. WHITE INVENTORS BY a ATTORNEY AGENT Patented Jan. 10, 1950 UNITED STATES PATENT OFFICE AN TISTATIC PHOTOGRAPHIC FILM Gale F. Nadeau and Walter R. White, Rochester, N. Y., assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application April 6, 1948, Serial No. 19,188

Claims. 1

This invention relates to photographic film and particularly to a film protected against static.

The accumulation of electrical charges on photographic film has been the cause of considerable trouble. These charges are produced by the friction of the film moving over rollers or past the gates of a camera and are manifested as irregular fogged patterns in the emulsion of the film after it has been developed. These static effects are particularly noticeable in a film provided with a cellulose nitrate support, although with the advent of high speed emulsions practically any film support will become sumciently electrified during manufacture or use so that the discharges of stored-up static electricity will affect the sensitive layer. Attempts have been made to overcome static in photographic films by the application of various layers to the film support. These layers have, in general, consisted of materials designed to dissipate the electric charges by providing the film with a conducting surface. Materials which absorb moisture and, therefore, provide a conducting surface have frequently been employed. These methods have not proven entirely satisfactory with the newer high speed emulsions and the absorption of water by the antistatic material is frequently objectionable.

The principal object of the present invention is to provide photographic films with layers rendering the films static-free. Another object is to describe the process of making static-free film. Other objects will appear hereinafter.

These objects are accomplished in the present invention by providing photographic films containing succinonitrile.

The figures of the accompanying drawings show in enlarged cross-sectional view the appearance of films constituting modifications of our invention.

According to our invention a photographic film support of a cellulose inorganic acid ester such as cellulose nitrate, or a cellulose organic acid ester such as cellulose acetate or cellulose acetate propionate is coated with a layer of succinonitrile. The anti-static material may be applied to the film support in various ways; for example, as a solvent wash on the rear side of the support following which the sensitive emulsion layer is coated on the opposite side. Similarly, a colloidal carrier material such as gelatin may be incorporated with the succinonitrile and coated on the rear surface of the film support or over the sensitive emulsion layer. In the latter case the gelatin layer containing the antistatic ma- 2 terial serves the dual purpose of protecting the emulsion layer from abrasion as well as eliminating static. If desired, the antistatic compound can be incorporated in the sensitive emulsion layer or in the support. We also contemplate as a part of our invention applying the antistatic layer to the surface of the film support contiguous to the emulsion layer in which case the compound may be incorporated in a subbing layer which is coated on the support before application of the sensitive emulsion layer. In the preferred embodiment of our invention we apply the antistatic layer to the rear surface of a film support such as cellulose acetate or on the surface of the emulsion layer. In other locations throughout the film the antistatic effect of the compound is decreased.

The antistatic material of our invention, succinonitrile, is unique as a material preventing static on photographic films. The material does not appear to depend for its effectiveness upon increasing the hygroscopicity of the surface of the film support, but the effect appears to be related more to the dielectric constant of the compound itself which is high compared to many other organic compounds. The compound is unique as compared to other organic chemicals of the same generic class-that is, other nitriles such as adiponitrile do not afford the static protection required for photographic films.

The following example is illustrative of the method of providing photographic films with the anti-static material of our invention.

A well esterified cellulose acetate film base was treated on the rear surface with succinonitrile by bead application of a 10% solution of succinonitrile in methyl alcohol, at 10 feet per minute so as to apply about 30 grams per sq. ft. The alcohol was evaporated from the film at a moderate rate leaving the anti-static material deposited on the film. A sample of the film base was tested by passing it over a static-generating surface and measuring the static charge on the surface. The charge was found to be very much lower than that generated under the same conditicns on a comparable cellulose acetate film base not provided with an anti-static backing. Following application of the anti-static layer a silver halide emulsion was coated on the other side of the film base. A roll of film thus treated was rapidly unwound at low humidity and developed. It was found to contain one-third as many static markings as a comparable film having no anti-static backing.

The amount of succinonitrile applied to the 3 film support is dependent upon a number of factors such as the static-forming characteristics of the particular film support or the sensitivity to static of the emulsion to be coated on the film support. We find that when the antistatic material is applied from methyl alcohol solution to the rear surface of a cellulose acetate film support, it suflices to use a solution containing the materialin a concentration of about 1 to 10 per cent. Concentrations of 1 to 3 per cent in a low viscosity solvent such as alcohol are not very 5 effective in preventing static but when the viscosity of the coating composition is increased by addition of a colloid such as' gelatin or cellulose acetate, the effectiveness of low concentrations is increased due to the increasein the thickness of layer which is obtainable at the same coating speed. Under such conditions the thickness of the antistatic layer can be about one per cent of the thickness of the support. When the antistatic material is applied to the support from.

solvent solution we select a solvent having limited solvent activity on the support, for example, an alcohol such as methyl alcohol is preferred when applying the material to a cellulose organic acid ester support, and ethylene dichloride is suitable when treating cellulose nitrate supports. A water solution of the compound which may contain gelatin sulfices when applying the antistatic layer over the emulsion layer.

Our invention is further illustrated in the accompanying drawings wherein Fig. 1 shows in enlarged cross-sectional view the appearance of a photographic film provided with the antistatic layer of the invention according to which sup port I0 is a cellulose ester support provided on one side with emulsion layer II and on the opposite side with the antistatic layer [2 of succinonitrile. Fig. 2 is a similar view of a film wherein support I0 carries the emulsion layer l I and the antistatic layer l3 of succinonitrile on the same side of the support.

It will be understood that our invention is ca pable of numerous variations and is to be taken as limited only by the scope of the appended claims.

What we claim is:

1. A light-sensitive photographic element comprising a cellulose ester film support carrying a silver halide emulsion layer and said element containing succinonitrile uniformly distributed in a layer thereof.

2. A light-sensitive photographic element comprising a cellulose organic acid ester film support carrying a silver halide emulsion layer and said element containing succinonitrile uniformly distributed in a layer thereof.

3. A light-sensitive photographic element comprising a cellulose acetate film support carrying a silver halide emulsion layer and an antistatic layer of succinonitrile.

4. A light-sensitive photographic element comprising a cellulose acetate film support, a lightsensitive silver halide emulsion layer on one side of said support. and an antistatic layer of succinonitrile on the opposite side of said support.

5-. A light-sensitive photographic element comprising a cellulose nitrate film support carrying a silver halide emulsion layer and said element containing succinonitrile uniformly distributed in a layer thereof.

GALE. F. NADEAU. WALTER R. WHITE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,380,940 Carroll et a1 Aug. 7, 1945 2,436,007 Kendall et a1 Feb. 17, 1948 

1. A LIGHT-SENSITIVE PHOTOGRAPHIC ELEMENT COMPRISING A CELLULOSE ESTER FILM SUPPORT CARRYING A SILVER HALIDE EMULSION LAYER AND SAID ELEMENT CONTAINING SUCCINONITRILE UNIFORMLY DISTRIBUTED IN A LAYER THEREOF. 